Route final texture setup sites through helper

docs/modernization/debt.md

@@ -18,6 +18,10 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. `NodeCanvas` density-resolve and
+  desktop VR UI `Texture` shader setup now route through
+  `legacy_canvas_draw_merge_services.h`; those paths still own render target,
+  sampler/texture binding, viewport/state restoration, and draw execution.
 - 2026-06-13: DEBT-0036 was narrowed again. `CanvasModeTransform::on_Draw`
   and `CanvasModeFloodFill::on_Draw` retained `Texture` shader setup now route
   through `legacy_canvas_draw_merge_services.h`; the mode paths still own

docs/modernization/roadmap.md

@@ -3051,6 +3051,10 @@ Results:
   share the retained draw-merge texture shader setup helper for `Texture`,
   `Tex`, and `MVP` setup. Texture/sampler binding, viewport/state setup, and
   draw execution remain in the node paths.
+- `NodeCanvas` density-resolve drawing and desktop VR UI drawing now share the
+  retained draw-merge texture shader setup helper, while render target,
+  sampler/texture binding, viewport/state restoration, and draw execution
+  remain in retained node/VR code.
 - `CanvasModeTransform::on_Draw` and `CanvasModeFloodFill::on_Draw` now share
   the retained draw-merge texture shader setup helper for `Texture`, `Tex`, and
   `MVP` setup. Active texture selection, sampler/texture binding, and draw

src/app_vr.cpp

@@ -475,9 +475,11 @@ void App::vr_draw(const glm::mat4& proj, const glm::mat4& camera, const glm::mat
             glm::translate(glm::vec3(0, 0, -1)) *
             glm::scale(aspect * tan_fov);
         sampler_linear.bind(0);
-        ShaderManager::use(kShader::Texture);
-        ShaderManager::u_int(kShaderUniform::Tex, 0);
-        ShaderManager::u_mat4(kShaderUniform::MVP, mvp);
+        pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader(
+            pp::panopainter::LegacyCanvasDrawMergeTextureUniforms {
+                .mvp = mvp,
+                .texture_slot = 0,
+            });
         set_active_texture_unit(0);
         uirtt.bindTexture();
         m_face_plane.draw_fill();

src/node_canvas.cpp

@@ -765,9 +765,11 @@ void NodeCanvas::draw()
         m_sampler_nearest.bind(0);
         set_active_texture_unit(0);
         m_rtt.bindTexture();
-        ShaderManager::use(kShader::Texture);
-        ShaderManager::u_int(kShaderUniform::Tex, 0);
-        ShaderManager::u_mat4(kShaderUniform::MVP, glm::ortho<float>(-1, 1, -1, 1));
+        pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader(
+            pp::panopainter::LegacyCanvasDrawMergeTextureUniforms {
+                .mvp = glm::ortho<float>(-1, 1, -1, 1),
+                .texture_slot = 0,
+            });
         m_face_plane.draw_fill();
         m_rtt.unbindTexture();
     }